1. Field of the Invention
The present disclosure relates to plastics, and more particularly to marking plastics for optical identification.
2. Description of Related Art
Plastics have gained widespread acceptance and are commonly found in food packaging, consumer electronics, and automotive applications. One consequence of the widespread use of plastics is the need to dispose of plastic objects—ideally through a recycling process. Recycling can enable the material forming discarded plastic objects to be reused in the manufacture of new plastic objects, thereby reducing virgin material in such objects. One challenge to recycling plastics is that some plastic materials are incompatible with other plastic materials, like styrene and polyethylene, where relatively small amounts of the first material intermixed with the second material can render the aggregated materials unsuitable for reuse. Recycling processes therefore generally sort plastic objects by composition, typically using optical systems that determine the composition of the object based on the spectral response of the plastic material to light. While generally satisfactory, some plastic materials can resist traditional optical sorting techniques due the composition of the plastic object. Dark plastic materials, for example, tend to exhibit insufficient spectral response to the light used in traditional optical sorting.
Such conventional methods and systems of plastic sorting have generally been considered satisfactory for their intended purpose. However, significant amounts of plastics can remain unidentified at the end of traditional sorting processes, so there is still a need in the art for improved systems and methods for determining the composition of plastic objects. The present disclosure provides a solution for this need.